Finally got my hands on my 1800 Icon A5, should be here shortly. Already ordered servos for it, thanks to the guys on this forum for brainstorming that topic. What size of motor would fit on this plane? I am aiming on using a 6s setup, Id like more power than required. Can you fit a 50mm or larger one? I cant seem to find a 6s compatible motor in this 40mm size range, but maybe im not looking hard enough. Any suggestions are appreciated!

Frustrated!! Tried three times today and couldn't get off the ground - and then the new Robarts nose gear ripped loose!! Lousy foam broke. Now I'm really frustrated. I have a G46 but the can dia. is too big at 50mm. Looking at the G32 but it comes in three flavors.530KV 600KV and 770KV. The 530KV takes a 12" prop, but to be honest I don't know what these numbers really mean other than revs per volt. Is the 530KV stronger than the 770KV? It has a 42mm dia. can so it may fit the motor mount. Just flailing around here! May just put it on the shelf. The little Seawind flys great but the Ventus is a pig! I'm thinking these foamys may not be my bag after 50 years of working with wood. Perhaps I should look at some wood plane kits that will take a little more abuse as I convert to E-Power.

Thanks Lupy - I will try the G32 770KV. Specs call for 3~4 cell battery so I don't think I should go to 6 cell for power. Intended to use the two 3000 Mah's I've got up front for balance, to get 6000 Mah for longer flights.
With the lousy weather I've devoted my time to the gliders I've got in the pipeline. The Icon should work well in the snow a little later. Willl build up the nose gear mounting with wood and re-balance. Maybe tape over for the time being.

Got the Icon all built and successfully maidened it. Im running a 60 sized motor with 6s and a 12x6x3 prop. Its so noisy, I love it! Here is a question for those of you that have built and flown theirs.......did anyone need to shim the motor up or down? When flying the Icon has a big tendancy to pitch down on throttle. It made for a very difficult landing since I had trimmed it so much up to compensate for that nose down attitude. I was reading about the CG and the rear prop and how it depends the line of thrust. I was thinking of putting some washers on the top part of the motor to effectively push the prop angle down towards the tail but perhaps the opposite would be true? Anyone experience this?

EDIT

I did some research on other rear prop planes and now I do in fact think the opposite is what I need. Tilt the motor up with washers at the bottom. If anyone can attest to this please chime in.

I disagree with Sentry. All of my high thrust line models do much better with the motor thrust line angled up to the front, looking from the rear of the model to the front of the model. Works on my large A5, works on my Seawind, works on my own design Skimmer, worked on my long ago scratch built Ken Willard Seamaster. Keth Sparks discovered the same thing on his Macchi M5 design.

If it is a tail mounted motor like a Polaris with the prop far back on the model, then the downthrust does work better than upthrust, generally.

Whe the prop is located roughly somewhere between the trailing edge of the wing and the leading edge of the wing, an up thrust line can do a lot to prevent nose overs at high power settings and low air speeds.

Also, with the T-Tail arrangement of the Icon, excessive downthrust as Sentry shows can affect the air blast on the horizontal tail, causing an additional nose down moment when power is applied, as the prop would be angled towards the bottom surface of the stab.

Images

Well, here is a question, can it work both ways and is it just maybe better one way? I shimmed the bottom of the motor mount using a APC prop adaptor so its a pretty significant shim and went to test it and it worked. It still noses down a bit at full throttle but at low to mid speeds it remains relatively level. This is a huge improvement from the maiden!!!! I could probably even shim it a bit more at this point but I wont be flying max speed a whole lot so I think ill just save my time and live with it.

On a side note, the flaps on this plane are great. I took off with 1/2 and it was awesome, saved the fuse from getting dinged up while getting up to speed on the icy snow, and on landing with full flaps it did wonderfully.

Taxiing this plane on the snow is a lot to be desired. It likes to want to turn right but hardly left at all. Exactly the opposite of my other plane I fly and taxi on the snow (which makes sense because of the thrust pull.) Odd. Heres a dumb question, I have the motor spinning clockwise (pilot's view), is this correct?

Going with the upthrust instead of the downthrust will likely fix the last of the issue. Redirecting the airflow from the prop from impinging from the bottom of the horizontal tail, which is an effect of the down thrust line. If you blow on the bottom of the tail, it will tend to nose down. Get rid of that effect and it will be even better.

With the Seabee and the Lake Renegade, the thrust line blows a little more on the top of the horizontal tail, helping to keep the nose up at low airpseeds and high power settings.

I'm glad my suggestion worked for you KLT. Thomas' example won't work (fully) bc he fails to see that his full scale examples wings are mounted on pods/pylons high above the wing centerline (which introduces other things that we won't get into, and the reason why the hor-stab on his 1st example is such an extreme angle). The biggest differece (and the one that matters the most) is that his examples the engine is almost directly over the CG. The A5s motor is on the chord line - TE of the wing (basically* level with the wings) and behind the CG. His examples are night/day different from the motor placement on the A5 and don't really apply here.

I'm glad my suggestion worked for you KLT. Thomas' example won't work (fully) bc he fails to see that his full scale examples wings are mounted on pods/pylons high above the wing centerline (which introduces other things that we won't get into, and the reason why the hor-stab on his 1st example is such an extreme angle). The biggest differece (and the one that matters the most) is that his examples the engine is almost directly over the CG. The A5s motor is on the chord line - TE of the wing (basically* level with the wings) and behind the CG. His examples are night/day different from the motor placement on the A5 and don't really apply here.

Sorry, but the Seabee example is not as you describe. The force arrangement is exactly as the Icon. I supplied the other examples to show that extreme downthrust on high mounted motors like the Easystar is not automatically the best way to go. The engineering is not made up. Further research on your part might well help you learn some new things....

in all seriousness, would this not be a scaling issue? There is a term for it, which eludes me atm, that refers to changes when a full scale design is scaled down.
I dont recall seeing a full scale pusher prop plane with exagerated thrust lines as we see in many scaled (and not so scaled )models.
I'm thinking in a way you are both correct...
Perhaps Thomas is correct with full scale & Sentry is correct with scaled flight?